Tuberculous pleural fluid is characterized by exudate, adenosine deaminase is elevated, and its sediment may be positive for Mycobacterium tuberculosis culture. Tuberculous pleural fluid is characterized by exudate. The appearance is turbid, and the specific gravity is more than 1.018. The proportion of mesothelial cells in the exudate is less than 5%, and the leukocytes are often more than 500*10^6/L, with lymphocytes being the main ones. Protein content is mostly greater than 40g/L; lactate dehydrogenase (LDH) content is elevated, and pleural effusion/serum LDH ratio is >0.6. In addition, tuberculous pleural fluid precipitation followed by tuberculosis culture can be positive, but the positive rate is low. Adenosine deaminase (ADA) can be elevated, mostly >45 U/L, and its sensitivity for diagnosing tuberculous pleural effusion is high. Increased gamma-interferon in tuberculous pleural fluid is also a feature. Typical systemic manifestations of tuberculosis, such as night sweats, afternoon hot flashes, malaise, and emaciation, as well as a strong positive PPD test, also help to suggest the diagnosis of tuberculous pleural fluid.